16 Questions
Which type of antigen is considered more effective based on size?
Bigger antigen molecules
What is an immunogen?
A substance that stimulates antibody formation
Which type of antigens provoke an immune response if transferred to a genetically different individual of the same species?
Histocompatibility antigens
What is a hapten?
A low molecular weight molecule
What are the structures recognized as foreign by the immune system called?
Antigenic determinants
How many epitopes or antigenic determinants does an antigen molecule typically have?
2
What is the characteristic of an immunodominant epitope?
It stimulates a greater antibody response
What is a small molecule that can bind with the antibody binding site but is not immunogenic unless attached to a larger molecular backbone?
Hapten
What is the major function of HLA typing in transplantation?
To measure alloreactivity
What does the term 'haplotype' refer to in the context of MHC genomic organization?
The total set of alleles on each chromosome
Which method of HLA testing uses the recipient's lymphocytes to determine reactivity against the donor's Class II antigens?
Mixed lymphocyte reaction
What does 'codominant alleles' mean in the context of MHC genomic organization?
Both alleles are expressed equally
What is the term used to describe the ability of a particular antibody to combine with a particular antigen?
Specificity
When some of the determinants of an antigen are shared by similar determinants on apparently unrelated molecules, what is this phenomenon called?
Cross-reactivity
What type of antibodies are termed heterophile antibodies?
Antibodies that react with unrelated plant or animal antigens
Which type of antigens are related to human blood group A and B antigens?
Bacterial polysaccharides
Study Notes
- Foreign substances with structures recognized as foreign by the immune system can be immunogenic or antigenic.
- Antigenic determinants or epitopes are structures on antigens that react specifically with antibodies or T lymphocyte receptors.
- An antigen is a molecule that interacts specifically with antibodies or T lymphocyte receptors, inducing an immune response when introduced into an animal.
- Epitopes consist of approximately 6 amino acids or 6 monosaccharides.
- Immunodominant epitopes stimulate a greater antibody response.
- Antigens have multiple epitopes and can be small molecules (haptens) or large macromolecules (proteins).
- Haptens are small molecules that cannot evoke an immune response on their own but can do so when conjugated to a larger carrier molecule.
- Antibodies are proteins produced by the immune system in response to specific antigens, recognizing and binding to their epitopes.
- The Major Histocompatibility Complex (MHC) is a genomic region important for determining compatibility between individuals, specifically in transplantation.
- MHC is located on chromosome 6 and consists of codominant alleles, each expressed by both parents and making up an individual's haplotype.
- HLA typing is used to determine compatibility for transplantation, with the closer match increasing the likelihood of a successful transplant.
- Serological and mixed lymphocyte reaction methods are used for HLA typing.
- Antibodies recognize epitopes on antigens through their combining sites, with some antibodies displaying cross-reactivity.
- Cross-reactivity occurs when determinants shared by different antigens cause the antibody to react with both.
- Heterophile antigens are antigens that exist in unrelated organisms but are structurally similar, leading to cross-reactivity in antibodies.
- The A and B blood group antigens are examples of cross-reacting antigens that are shared between humans and certain bacteria.
- Cross-reacting antibodies are termed heterophile antibodies.
- Functional assays, such as the heterophile antibody test, are used to measure alloreactivity, with heterophile antibodies being the most sensitive but taking several days to complete.
Test your knowledge of antibody specificity and the immune response with this quiz. Explore the production of IgM and IgG antibodies, as well as the concept of antigen-antibody specificity.
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